Low-rate spread spectrum communication transmission base band system

Abstract

The invention relates to a low-rate spread spectrum communication transmission base band system. The system is characterized by using an FPGA (field-programmable gate array) and a DDS (direct digital synthesizer) to realize the low-rate spread spectrum transmission base band system with settable parameters. The system specifically comprises an FPGA chip, a DDS chip and a peripheral module, wherein the FPGA chip comprises a clock signal generating module, an RS (recommended standard)-232 serial communication module, a central control module, a framing module, a channel coding module, a PN (pseudo noise) code generator module, a digital shaping filter module and a DDS working condition controller; the DDS chip comprises a phase accumulator module, a waveform ROM (read only memory) module, aD / A conversion module and a lowpass filtering module and is used for D / A conversion and signal modulation; the input / output port of the FPGA chip is connected with the input port of the DDS chip; andthe FPGA chip inputs the data to be modulated and the condition control signal to the DDS chip and controls the working mode of the DDS chip.

Description

technical field [0001] The invention relates to a communication transmitting baseband system, in particular to a low-rate spread spectrum communication transmitting baseband system. Background technique [0002] Spread spectrum communication is a method of information transmission, and its basic feature is to use a pseudo-random code that is many times higher than the transmitted information data rate to expand the spectrum of the baseband signal carrying information data to form a broadband low power spectral density. The signal is transmitted, and the frequency bandwidth occupied by the signal is much larger than the minimum bandwidth necessary for the transmitted information. Because spread spectrum communication has the advantages of good anti-interference performance, security and confidentiality, multi-access communication, good anti-fading and anti-multipath, etc., it has widely penetrated into all aspects of communication, such as satellite communication, mobile comm...

AI Technical Summary

Problems solved by technology

[0005] The purpose of the present invention is to overcome the limitations of the current spreading code rate and spreading code length of the current spreading chip, and the shortcomings such as inability to correct and detect errors, limit the application in some spreading systems, thereby proposing a low-rate spreading Communication Transmitting Baseband System

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